DC ElementWertSprache
dc.contributor.advisorFerber, Torben-
dc.contributor.advisorHaller, Johannes-
dc.contributor.authorDreyer, Sascha Simon-
dc.date.accessioned2024-02-26T09:28:32Z-
dc.date.available2024-02-26T09:28:32Z-
dc.date.issued2023-12-21-
dc.identifier.urihttps://ediss.sub.uni-hamburg.de/handle/ediss/10726-
dc.description.abstractPhenomena such as dark matter can be connected to the standard model via additional spin-0 mediators. This doctoral thesis describes a search for a long-lived spin-0 particle S in rare B-meson decays mediated by b → s quark transitions. A dataset corresponding to an integrated luminosity of 189fb−1 of e+e− collisions collected at the Υ(4S) resonance energy by the Belle II experiment is analysed. The search is carried out in eight exclusive channels, the two modes of production B+ → K+S and B0 → K∗0 S with decays via S → e+e−/μ+μ−/π+π−/K+K−. Decays of the S to standard model particles are motivated if the decay to dark matter is kinematically not possible. Mediator masses between (0.025 − 4.78) GeV/c2 and lifetimes between (0.001 − 400) cm are probed. Long-lived particle reconstruction is studied and validated with K0S-mesons. Maximum likelihood fits to the reconstructed S mass distribution are S used to determine the signal yield. No evidence for the signal process is found. Model-independent upper limits are derived on the branching fractions of the signal processes. The upper limits extend down to the order of O(10−7). These are the first constraints on hadronic final states of the S produced in B → KS and the most stringent bounds from a direct search for S → e+e− at e+e− colliders. The results are interpreted in models that predict a dark Higgs-like scalar and an axionlike particle with fermion couplings. The model-dependent bounds are competitive with existing experimental constraints.en
dc.language.isoende_DE
dc.publisherStaats- und Universitätsbibliothek Hamburg Carl von Ossietzkyde
dc.rightshttp://purl.org/coar/access_right/c_abf2de_DE
dc.subject.ddc530: Physikde_DE
dc.titleSearch for a long-lived spin-0 particle in b → s quark transitions at the Belle II experimenten
dc.typedoctoralThesisen
dcterms.dateAccepted2023-12-21-
dc.rights.cchttps://creativecommons.org/licenses/by/4.0/de_DE
dc.rights.rshttp://rightsstatements.org/vocab/InC/1.0/-
dc.subject.gndElementarteilchenphysikde_DE
dc.subject.gndDatenanalysede_DE
dc.subject.gndBelle-II-Detektorde_DE
dc.subject.gndDunkle Materiede_DE
dc.type.casraiDissertation-
dc.type.dinidoctoralThesis-
dc.type.driverdoctoralThesis-
dc.type.statusinfo:eu-repo/semantics/publishedVersionde_DE
dc.type.thesisdoctoralThesisde_DE
tuhh.type.opusDissertation-
thesis.grantor.departmentPhysikde_DE
thesis.grantor.placeHamburg-
thesis.grantor.universityOrInstitutionUniversität Hamburgde_DE
dcterms.DCMITypeText-
datacite.relation.IsSupplementedBydoi:10.1103/PhysRevD.108.L111104de_DE
dc.identifier.urnurn:nbn:de:gbv:18-ediss-115439-
item.advisorGNDFerber, Torben-
item.advisorGNDHaller, Johannes-
item.grantfulltextopen-
item.languageiso639-1other-
item.fulltextWith Fulltext-
item.creatorOrcidDreyer, Sascha Simon-
item.creatorGNDDreyer, Sascha Simon-
Enthalten in den Sammlungen:Elektronische Dissertationen und Habilitationen
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